BR0007868B1 - apparatus for filtering paper pulp. - Google Patents

Abstract

Process for the filtration of paper pulp with a device that comprises a rotor and a stator; one of the two, filter (1), has perforations of slot or hole types, and the other, the backwashing element, includes means that are intended to generate pressure pulses that consist in combatting the gradual clogging of the perforations of the filter and the gradual flocculation of the pulp during the creep of the pulp between the rotor and the stator by creating deflocculation zones and/or increasing the relative speed between the pulp and the backwashing elements.

Description

DESCRIPTIVE REPORT

Patent of Invention for "PAPER FILTERING DEVICE"

The present invention relates to the problems of paper mass filtration and, more particularly, paper mass from old paper pulp.

It is known in paper mass technology to employ various filtration apparatus, either to eliminate foreign matter, to classify the fibers of the paper mass according to their lengths, or to increase the concentration of the paper mass by eliminating Water.

Known filtration apparatus includes filters comprising a rotor and a stator, one of which, hereinafter referred to as the filter, and having openings, such as cracks or holes, and the other, hereinafter referred to as the backwater collecting tank, occupying a function. clearing and including means for generating pressure pulsations to prevent blockage of openings. The sieve can therefore be fixed or rotating, and conversely, the water-collecting tank around it is rotatable with a fixed sieve, and fixed with a rotating sieve. In addition, the liquid may flow through the sieve from the outside in the inward direction (toward the axis), which is said centripetal operation, or from the inside towards the outside, said centrifugal operation.

Within this type of apparatus, the mass reaches one end of the cylindrical sieve, flows into the space comprised between the cylindrical sieve and return water catcher, and exits again at the other end.

As the mass advances inside the filter, it becomes thicker and thicker.

This progressive mass thickening produces several effects: a mass flocculation effect and a sieve obstruction effect.

Even if the admitted mass is preliminarily well deflocated, there is a risk of flakes appearing during their advance; The higher the flocculation, the more significant the obstruction. If the return water collection tank rotates, there is a tendency to drag the mass with its rotation. If the return water collection tank is fixed, it is the filter that has the tendency to drag the rotating mass. In both cases, as the clearing effect of pressure pulsations caused by the return water collection tank is directly linked to the speed difference between the return water collection tank and the mass, the more mass advances in the sieve end direction, the less Effective is clearing at the same time that the sieve tends to clog the most.

On the other hand, with a thin slit screen, long fibers will be more difficult to pass than short fibers, and therefore the ratio of long fibers to short fibers increases as the mass advances, which in turn accelerates the flocculation process and the obstruction process.

The result of this accumulation of phenomena is a progressive reduction in the production per sieve surface unit with the damascus advance within the filter.

Many patents have been aimed at combating this progressive reduction in filter productivity by intervening in the course of the long sieve path in order to create areas of strong deflocculation and / or mass reduction.

In particular, since 1968, in his French patent 1,539,846, the proponent proposed the use of obstacles in order to eliminate the liquid velocity parallel to the sieve surface.

In US 4,383,918, the arrangement between the sieve and the rotor for obstacles causing turbulence is proposed.

In FR 2,613,390, also in the name of the depositor, it is proposed to separate the sieve into several portions and to introduce dilution water between portions of the sieve.

In British patent GB 2,222,967, it is proposed to install two sieves separated by fixed fins placed between the sieve surface and the rotor.

All of these devices gradually improved the operation of filtration apparatus consisting of a sieve and a return water collecting tank, but still insufficiently. According to the present invention:

the speed difference increasing zone may comprise one or more baffles;

- The deflocculation zones and the increase in speed difference may be combined.

The present invention relates to a type filtration apparatus having a cylindrical sieve and a return water collecting tank with paddles which produce pressure fluctuations to combat the obstruction of said sieve, said sieve and said rotorpus having , in at least two parts, substantially equivalent diameters, these portions being separated from each other by means whose purpose is to eliminate the liquid velocity parallel to the surface of the sieve, and to create turbulence, characterized in that said means are the baffles constituted in one part by the cavities disposed in a annular crown of the trap disposed between said portions of the sieve and, in the other part, by an annular deflector carried by the return water collecting tank opposite the sieve crown carrying the cavities, such that the largest part of the liquid flow is forced through the cavities.

The present invention may furthermore comprise all or part of the following devices taken together or separately:

a - the sieve comprising a ring stack,

(b) the sieve consisting of a stacking of crates, each being obtained by juxtaposition of wires, being substantially parallel to the rotor axis of rotation, perpendicular to this axis, or even inclined,

c - the sieve comprising a stack of hollow or slotted plates;

d - the different parts of the sieve being constituted differently from each other,

and - the cavities being parallelepiped shaped,

f- the cavities being of hollow cylindrical volumes,

g - certain cavities being connected to a dilution channel, h - the return water collecting tank being a cylinder also equipped with annular deflectors that the sieve annular cavity crowns contain, the said return water collecting crowns are replaced in the face of the cavities so as to form with them a plurality of Dechicanes

i - the number, type, thickness and inclination of the blades carried by the return water collecting tank may vary between the annular deflectors,

- the apparatus further comprising a violent stirring zone disposed at the entrance of the sieve;

k - the turbulence within the violent agitation zone disposed at the entrance of the sieve being created by the fins fixed over the return water collecting tank and the fins fixed over the sieve.

The present invention therefore relates to an apparatus for treating paper pulp whereby each part of the filtration apparatus comprises an outlet of the admitted products, each annular sieve crown possibly containing a dilution inlet, the filtration apparatus further comprising: an inlet and an outlet of the tailings which works by regulating the outlets of the admitted products, the tailings outlets and the dilution inlets through the pipelines, and may reduce the rate of return water collection tank so that it is as low as possible, In order to save energy while maintaining a small consumption of tailings.

An embodiment of the apparatus according to the invention may comprise the following features:

(a) adjustment of the rotor speed as a function of the mass pressure difference between the input of the appliance and at least one of the permitted outputs;

(b) adjustment of the rotor speed as a function of consumption (s) within at least one of the permitted product outlets;

(c) adjusting the rejection rate of one or more parts of the screen by adjusting the output of the appliance leakage during permitted consumption and dilution consumption, (d) a combination of two or three of these adjustment means.

The present invention is also directed to the manufacture of the above described media for filtering paper pulp.

By way of non-limiting examples and to facilitate understanding of the invention, the accompanying drawings are given:

Figure 1: A first example of embodiment comprising a zone of reduction obtained by means of baffles.

Figure 2: A sectional view according to AA of Figure 1.

Figure 3: A variant embodiment of Figure 1.

Figure 4: A second embodiment of Figure 1.

Figure 5: A second embodiment according to the invention, combining a deflocculation zone and a shrink zone according to Figure 1.

Figure 6: A third embodiment using the deduction means of Figure 1, on a centripetal filter.

Figure 7: A perspective view illustrating a sieve according to the invention.

Figure 8: A perspective view illustrating the rotor intended to be placed within the screen of Figure 7.

Figure 9: A partial perspective view showing the interior of the screen of Figure 7.

Figures 10 and 11: Two large-scale partial views of Figure 9.

Figure 12: A partial view of the interior of a screen realization variant of Figures 7, 9, 10 and 11.

Figure 13 is a partial view of an embodiment of a filter element according to the invention.

Figure 14 is a partial view of another embodiment of a filter element screen according to the invention.

Figure 15 is a vertical sectional view of a filter element according to the invention.

Figure 16: An exemplary embodiment of a filtration apparatus. In all Figures 1 to 6, the sieve is constituted, as described in patent application EP 0 707 109, by a stack of bristles 1 in a U-section, pressed down. against each other by means of two crowns 2 and 3 joined together by the strands 4 which allow the pre-tightening. The bases of the U are provided with openings (which are crevices or holes).

The mass arrives at the filter from its end to the left of Figure (on the side of crown 2) and exits again from its opposite end (on the side of crown 3) circulating within the space 6 between the surrounding water collecting tank 5 and the screen as indicated by arrow fl.

It should be noted, however, that the invention is not limited to this particular sieve structure, but is applicable to any cylindrical sieve as will be described below.

According to the invention a speed decreasing zone is created in which the mass is dragged.

Within this objective, as illustrated in Figures 1 and 2, a series of baffles are arranged in the sieve that slow down the rotational movement of the mass.

Referring to these Figures, it is seen that in the replacement of an ear circles 1 with a plurality of divisions 20, parallel to the axis of the filter, that with the edges of the two rings 1 which frame them constitute a plurality of parallelepiped shaped cavities C which are arranged along the entire contour of the sieve.

In front of these divisions 20 an annular division 21 is arranged perpendicular to the axis of the filter and carrying the rotor 5.

Thus, as shown by arrow f2, the mass flow is deflected by annular separation 21 and collides with divisions 20 which are connected to the screen and pass through cavities C to return into space 6.

This causes a decrease in the rotation speed of the mass and, at the same time, agitation of the mass which has a deflocculating and fluidizing effect. A fluidized, agitated, flapless state that favors flow within the openings, holes is understood. or cracks in the plait.

It follows that the sieve is divided into two parts; a first part above the crown of cavities C and a second part below, of these two parts being separated from each other by the crown of cavities C.

It also follows that the rotor is divided into two parts by circular division 21.

In Figure 1, baffle 20/21 is arranged in the middle of the sieve; In Figure 3 it is arranged near the end, that is, where the obstruction effects are most significant due to the thickening of the mass.

Figure 4 brings together the arrangements of Figures 1 and 3.

According to the example illustrated in Figure 5, the turbulences are further created by the fins 10 attached to the surrounding water collecting tank and the fins 11 attached to the sieve.

These IOell fins may be radial or inclined and may have inclinations in opposite directions.

Preferably, as shown in Figure 5, the shapes of the fins 10/11 are such that they overlap one another.

In this way, in the area where the fins are located, a violent agitation which causes a good deflocculation of the mass is achieved.

Figure 6 is a centripetal filter using the means of Figure 1. Same elements bearing the same references.

Over this Figure, the sieve 1 is located within the return water tank 5. The mass arrives at the end of the sieve and in the space 6 located between the sieve 1 and the surrounding water collection tank 5.

Within a sieve area 1, the U-section circles are replaced by divisions 20, parallel to the cylinder axis, and the return water collecting tank 5 comprises an annular division 21.

As in the case of Figure 1, the mass is offset by the annular division 21 and collides with the divisions 20. Figures 7 to 17 represent a variant embodiment of the apparatus according to the present invention.

Figure 7 shows a cylindrical sieve 30 which is constituted by bars 31 arranged vertically next to each other, with a slight game (between 0.05mm and 1m) and fixed on the horizontal crowns 32,33, 34, 35, 36 and 37.

Crowns 32 to 37 are traversed by tie rods 38, parallel to the cylinder shaft, these tie rods 38 being attached to the crowns of ends 32 and 37, so that the assembly is held by tightening tie rods 38.

Figure 8 represents the rotor 4Θ which is placed inside the screen of Figure 7. This rotor is a cylinder having three annular crowns41, 42 and 43. Within the areas between the annular crowns are the blades 45, commonly known as "blade blades". drainage "in the paper pulp industry.

Drainage blades 45 will function to cause pressure / depression thrusts that tend to prevent sieve clogging.

Crowns 41 to 43 are arranged on the rotor so that they face crowns 33, 34 and 35.

It will be explained later how crowns 33, 34 and 35 of sieve 30 cooperate with rotor crowns 41, 42 and 43 to form baffles.

As shown in Figure 8, annular crowns 41, 42 and 43 define four areas of rotor 40.

The shape, number and inclination of the drainage paddles or blades45 may vary from zone to zone.

Figure 9 represents the sieve of Figure 7 viewed from inside.

Crowns 33, 34 and 35 are seen to be designed to define C-ascavities.

Within this example, as the sieve 30 is made of small juxtaposed bars 31, the cavities C are not made as in the case of Figures 1 to 6 where the sieve is U. As shown in Figure 9, the crowns 33, 34 and 35 they are constituted by a ring comprising a multitude of parallelepiped cavities having substantially the same shape as the cavities C of Figures 1 to 6.

Certain wells C of crowns 33 and / or 34 furthermore contain holes which are connected to dilution arrival channels 50.

Figures 10 are the detail views, on a larger scale. Figure 9.

Figure 12 illustrates a variant whereby, instead of disposing of the parallelepiped-shaped cavities C, the cylindrical cavities or holes are not disposed through the cavities D, certain of which can be connected to the channels 50.

As shown in Figure 12 (holes not completely through cavities D) and Figure 13 (parallelepiped shaped cavities C) the rotor annular crown 41 (42, 43) cooperating with crown 33 (34, 35) is disposed with practically level with the middle of the wells C or cylindrical holes D.

Arrow F illustrates how the mass coming from under the crown 33, 41 is forced into a cavity C or D, this cavity and the crown41 forming a baffle that considerably slows the velocity of the mass.

It is seen from these Figures that the caps 31 are held by the arches 31a.

Figure 14 illustrates another embodiment in which the same elements carry the same references.

Within this example, the sieve 30 is fixed and disposed outside the rotor 40 carrying the drainage blades 45. The crown 41 of the rotor 40 is facing the crown 33 of the sieve 30 so that the cavities C of said crown 33 form with the annular crown 41 a series of baffles.

In this Figure, at the bottom of cavity C comes a channel 50 which is a water channel.

This allows combining the diminishing action caused by the C-baffles with a mass diluting action, which has a tendency to gradually thicken as it passes through the filter apparatus. Referring to Figure 16, it is seen that the filter element agrees with the invention can include, from top to bottom:

an upper end crown 32 for sieve 30;

an intermediate crown 33 having a plurality of decavities C, some of which are connected to dilution channels 50;

- a second intermediate crown 34, analogous to crown 33;

- a lower end crown 37, attached to the standing crown 32, not shown;

- an annular crown 41, carried by the rotor, and located opposite the cavities C of the crown 33 to define with it a plurality of baffles;

- a second annular crown 42 carried by the rotor located opposite the cavities C of the crown 34.

The sieve 30 and the rotor 40 are thus divided into three zones X, Y and Z and starting from the base.

The mass to be purified arrives at Q at the base of the device.

Zone X has an outlet 60 for so-called "admitted" products, meaning those which may pass through sieve 30; zone Y has an exit 61 for admitted products and zone Z an exit 62 for admitted products.

It is quite evident that the mass has a tendency to thicken and flush as it moves from one zone to another.

As has already been said, thickening causes a low clogging efficiency which must be compensated for, for example, by a higher speed and therefore with a more significant energy consumption. The introduction of water in the channels 50 which flow into certain Cou D cavities of the crown 34 and the crown 33 allows to contain this thickening, and thus reduces the rotor speed and therefore saves energy.

At its top, the apparatus has a lid 63, an output R for the tailings.

Rotor speed 40 may be adjusted as a function of the pressure differential between the inlet Q within the apparatus and at least one of the prevailing pressures within the outlet channels of the admitted products 60, 61, 62. The rotor speed may also be adjusted. 40 depending on one or more of the consumptions within the pipes 60, 61 or 62.

In either case this allows to reduce the rotational speed of rotor 40 and therefore to realize energy savings.

The sieve can be realized in multiple ways, either by stacking the rings in the U-section of Figures 1 to 6, or by stacking the grids obtained by juxtaposing the bars of Figures 12 and 13, or by stacking the perforated orifice or slotted plates of the Figure. 15

Thus, for example, they may consist of the plates 70 into which the slots 71 with circular drills are cast, the slots being then made with circular saws.

It should be noted that by arranging the inclined clearance blades 45 a suction outlet is obtained which accelerates circulation within the apparatus.

It should therefore be noted that, since rotor 40 is divided into portions, sieve 30, it is possible for each portion of the rotor to use blades 45 which are different in number, shape and inclination.

Similarly, the different portions of the sieve may be different constitutions.

In all the examples shown, the edges of the C or D cavities are at exactly the same level as the inner wall of the sieve 30.

It is possible to arrange them so that they exit slightly from the interior of the sieve 30, but on condition that this does not prevent the introduction of the rotor 40 into the sieve 30, i.e. the annular crowns such as 41, 42, etc ... can pass.

Claims (15)

1.- Paper mass filtering apparatus, of a type which comprises a cylindrical sieve (30) and a return water collecting tank (40) fitted with paddles (45) which produce pressure fluctuations to counteract the obstruction of said sieve said screen (30) comprising at least two portions of approximately equivalent diameters which are separated from each other by means for the purpose of eliminating the velocity component of the liquid parallel to the surface of the screen and creating turbulence, characterized in that said means are baffles which are comprise, in one part, cavities (C, D) arranged in an annular crown (33, 34, 35) of the sieve disposed between said portions of the sieve, and in another part, an annular deflector (21, 41, 42, 43) arranged in the return water collecting tank facing each other so that all liquid flow is forced through such cavities. 2. A paper filter device according to Claim 1, characterized in that the sieve (30) comprises a stack of rings. 3. A paper mass filtration apparatus according to claim 1, characterized in that the sieve (30) comprises a stack of grids, each grid being obtained by juxtaposing wires (31), which are substantially parallel to the rotor axis of rotation (40). ), whether perpendicular to this axis or even inclined. 4. A paper filter device according to claim 1, characterized in that the sieve (30) comprises a stack of cylindrical orifice or slotted plates. 5. A paper mass filtration apparatus according to claim 1, characterized in that the different parts of the sieve (30) are constituted differently from each other. A paper mass filtration apparatus according to any one of claims 1 to 5, characterized in that the cavities are parallelepiped shaped (C). A paper filter device according to any one of claims 1 to 5, characterized in that the cavities are cylindrical hollow volumes (D). A paper filter device according to any one of claims 6 or 7, characterized in that certain cavities are connected to a dilution channel (50). 9. A paper filtration apparatus according to any one of claims 1 to 8, characterized in that the number, type, thickness and inclination of the paddles (45) carried by the surrounding water collecting tank (40) may vary from one to another. the annular deflectors (41, 42, ...). A paper filter device according to any one of the preceding claims, characterized in that it further comprises a violent agitation zone disposed at the entrance of the sieve. 11. A paper mass filtration apparatus according to claim 10, characterized in that the turbulences within the violent agitation zone disposed at the inlet of the sieve are created by the fins (10) attached to the return water collecting tank and the fins. (11) fixed on the sieve. 12. A paper-filtration device according to claim 1, characterized in that each part (X, Y, Z) of the filtration apparatus comprises an outlet of the admitted products (60, 61, 62), each annular crown (33). 34) of the sieve (30) possibly containing a dilution inlet, the filter apparatus also having an inlet Q, an outlet R of the tailings and the channels (50). 13. A paper mass filtration apparatus according to claim 12, characterized in that the speed of the return water collection tank (40) is adjusted as a function of the pressure differential between the inlet (Q) of the apparatus and at least one of the pressures. within the exit channels (60, 61, 62) of the admitted products. 14. A paper filtration apparatus according to claim 12, characterized in that it adjusts the speed of the return water collection tank (40) as a function of at least one of the consumptions within the outlet channels (60, 61, 62). of the admitted products. 15. A paper mass filtration apparatus according to claim 12, characterized in that it adjusts the rejection rate of one or more parts of the sieve by adjusting the waste output of the apparatus taking into account the allowable consumptions and os. dilution consumption.